This invention relates to an electric distribution box which contains an ECU (Electric Control Unit), and is mounted within an engine room of an automobile.
FIGS. 7 and 8 show related electric distribution boxes, respectively (see JP-A-2002-159116 (Pages 2 to 4, FIG. 2) and JP-A-2003-95036 (Pages 2 to 4, FIG. 2), for example). The electric distribution box (JP-A-2002-159116) 50, shown in FIG. 7, is an automotive electric distribution box for supplying electric power to door lock devices and others, and this electric distribution box 50 is designed such that at the time of collision of the vehicle, damage to the electric distribution box 50 is kept to a minimum so as to protect an internal circuit so that the supply of electric power to the loads can be maintained as much as possible. A projecting portion 52 for preferentially receiving an impact upon collision of the vehicle is provided at a box body 51 which is mounted on a cowl side panel (not shown) disposed rearwardly of an instrument panel. Also, mounting brackets 53 for being preferentially broken by an impact upon collision of the vehicle are provided at the box body 51.
The electric distribution box 50 comprises the box body 51, and various electronic parts (not shown) and so on contained in the box body 51. The box body 51 is resin-molded into a rectangular shape, and a parts-receiving chamber for receiving the various electronic parts and so on is formed within the box body 51. The projecting portion 52 projects from a side wall of the box body 51 in a direction to receive an impact upon collision of the vehicle. Vertical ribs 52a for reinforcing purposes which extend in a direction parallel to the impact-receiving direction, as well as horizontal ribs 52b for reinforcing purposes which perpendicularly intersect the vertical ribs 52a, are formed at the inner side of the projecting portion 52, and the stiffness of the projecting portion 52 is increased by these ribs.
The pair of mounting brackets 53 are provided respectively at corner portions of the side wall of the box body 51 in opposed relation to each other in a diagonal direction. Each of these mounting brackets 53 includes an arm 54 extending from the side wall, and a mounting portion 55 extending from the arm 54. Each arm 54 is reinforced by ribs 54a, but is disposed in intersecting relation to the impact receiving direction, and therefore is adapted to be broken prior to the breaking of the electric distribution upon collision of the vehicle. The mounting portion 55 has a screw hole 55 formed therethrough at a center thereof, and also has radial ribs formed around the screw hole 55 at equal intervals. Screws are passed respectively through the screw holes 55, and are tightened, thereby fixing the box body 51 to the cowl side panel (not shown).
The related example (JP-A-2003-95036), shown in FIG. 8, is the electric distribution box 60 which contains an ECU, and is designed to prevent the ECU from being broken upon collision of the vehicle, thereby enhancing a safety. In this electric distribution box 60, the ECU 63 (which is higher in rigidity than a box body 61) is mounted in this box body 61 (fixedly mounted within an engine room) through mounting portions 66, and the mounting portions 66 are provided in a projecting manner so that the ECU 63 can be disengaged from the box body 61 by an impact upon collision of the vehicle.
The electric distribution box 60 comprises the box body 61 made of a synthetic resin, and the ECU 63 contained in the box body 61. The box body 61 is fixed in a space, for example, between a headlamp and a suspension tower within the engine room. Engagement grooves 62 are formed in a side wall of the box body 61, and flanges 66a, formed respectively at distal ends of the mounting portions 66 of an outer casing 65, are retainingly engaged in the engagement grooves 62, respectively.
The ECU 63 includes an ECU body 64 contained in the outer casing 65 made of aluminum. The mounting portions 66 for mounting on the box body 61 are formed on and project from opposite side surfaces of the outer casing 65, respectively. The flange 66a, serving as a retaining portion, is formed at the distal end of each mounting portion 66. When the mounting portions 66 receive an impact upon collision of the vehicle, the mounting portions 66 are broken prior to the breaking of the electric distribution box 60. As a result, the ECU 63 is disengaged from the box body 61, and escapes into an unoccupied space, and therefore the ECU body 64 will not be broken even when the box body 61 is broken, thereby maintaining the minimum electrical function.
Other related example is disclosed in JP-UM-A-6-31327 (Pages 4 to 6). This related example relates to an electric distribution box mounted inside an instrument panel, and is designed such that the electric distribution box will not project into a vehicle room at the time of collision of the vehicle. A support cancellation portion for positively canceling support upon reception of an impact at the time of collision of the vehicle is provided at at least one of mounting brackets formed respectively at front and rear sides of the electric distribution box. The electric distribution box whose support has been canceled drops downward, so that the electric distribution box is prevented from breaking through the instrument panel into the vehicle room.
However, the above related electric distribution boxes 50 and 60 have the following problems to be solved. In the first related example, when the arms 54 are broken by an impact upon collision of the vehicle, the electric distribution box 50 escapes in a predetermined direction, so that the electric distribution box 50 is prevented from being crushed. However, the direction of escape of the electric distribution box is not limited, and therefore there was a fear that the electric distribution box 50 was crushed together with the vehicle body when the electric distribution box escaped in some direction.
In the second related example, the ECU 63 of high rigidity is contained in the box body 61, and when the mounting brackets 66 are broken upon collision of the vehicle, the ECU 63 can be disengaged from the box body 61. In this case, also, there was a fear that the ECU 63 was crushed together with the vehicle body when the EUC 63 escaped in some direction as is the case with the above related example. And besides, the ECU 63 is supported in a floating condition by the mounting portions 66, and therefore the stability of the ECU was bad, and there was a fear that the ECU vibrated during the travel of the vehicle.
In the third related example, the electric distribution box whose support has been canceled drops downward, so that the electric distribution box is prevented from breaking through the instrument panel into the vehicle room. However, the direction of movement of the electric distribution box after this dropping movement is not limited, and therefore as is the case with the first and second related examples, there was a fear that the electric distribution box was crushed when the electric distribution box moved (or escaped). in some direction.